The miniaturization of imaging devices is progressing. Imaging devices are primarily composed of a lens and an imaging sensor. In order to form an image of a subject on an imaging sensor in an imaging device, the distance between the lens and the imaging sensor may need to be adjusted depending on the distance between the subject and the imaging device. Conventionally in such cases, the distance between the lens and the imaging sensor is adjusted, for example, by moving a lens coupled to a focal length adjusting device using an actuator such as a motor. However, with this configuration, there is a problem in that the configuration of the focal length adjusting device for moving the lens via the motive power of a motor becomes complex and miniaturizing the imaging device becomes difficult.
In addition, Unexamined Japanese Patent Application KOKAI Publication 2003-215429 discloses a technology wherein the distance between a lens and an imaging sensor is adjusted by moving a lens holder using an actuator composed of an electrostrictive material.
This lens driving mechanism results in a construction that is simpler than that of a lens driving mechanism that uses an electromagnetic motor or similar device. However, guides or springs are needed to control the flexing of the electrostrictive material. For this reason, there are many component parts, and construction remains complex.
Instead of varying the position of the lens, lenses (lens systems) whose focal lengths can be varied are also being used. These types of lens systems comprise a plurality of single lenses. By mutually varying the positions thereof, the focal length of the lens system is varied. However, the configuration whereby the single lenses are moved in order to vary the focal length is identical to that of the above lens driving devices. Consequently, the configuration of conventional lens systems is complex, and focal length adjustment is difficult.